 Centre National de la Recherche Scientifique  Institut National Polytechnique de Grenoble  Université Joseph Fourier Laboratoire G-SCOP 46, av Félix Viallet Grenoble Cedex ROMMA Task 1 Geometric Model Processing Status Briefing Ahmad Shahwan - Gilles Foucault - Jean-Claude Léon G-SCOP Laboratory Université de Grenoble, Grenoble-INP April 2011

Extracting functional denominations of components given the solid model of the product. Motivation

Data Flow Diagram Maximal Surface/Edges Detection STEP File Geometric Interaction Detection Unique B-Rep Model Generation of Homographs 3D Geometric CI Graph Conventional Interfaces Taxonomy Elimination of Homographs Using Ref State 1 Functional Designations Taxonomy Function CI Graph (all possible homographs) Matching with Functional Designations Functional Designations (multiple suggestions) Annotated ModelUser Functional Designations Interpretations Internal Efforts Screws Elimination of Homographs Using Ref State 2 Kinematic Screws Kinematic Constraints Function CI Graph (less homographs) Eliminating Multiple Candidates Functional CI Graph (least homographs)

Data Flow Diagram Maximal Surface/Edges Detection STEP File Geometric Interaction Detection Unique B-Rep Model Generation of Homographs 3D Geometric CI Graph Conventional Interfaces Taxonomy Elimination of Homographs Using Ref State 1 Functional Designations Taxonomy Function CI Graph (all possible homographs) Matching with Functional Designations Functional Designations (multiple suggestions) Annotated ModelUser Functional Designations Interpretations Internal Efforts Screws Elimination of Homographs Using Ref State 2 Kinematic Screws Kinematic Constraints Function CI Graph (less homographs) Eliminating Multiple Candidates Functional CI Graph (least homographs)

STEP File ISO Standard. AP203 allows the representation of the geometry of the product in a standard textual format using Boundary Representation (B-Rep). ISO ; HEADER; FILE_DESCRIPTION(('a Product shape'),'1'); FILE_NAME('Euclid Shape Model',' T11:31:03',('Author Name'),( 'MATRA-DATAVISION'),'OL-2.0B','EUCLID','Authorisation status'); FILE_SCHEMA(('AUTOMOTIVE_DESIGN_CC1 { }')); ENDSEC; DATA; #1 = PRODUCT_RELATED_PRODUCT_CATEGORY('Undefined Category','Undefined De scription',(#2)); #2 = PRODUCT('the product name','the product name','void',(#3)); #3 = MECHANICAL_CONTEXT('Mechanical',#4,'Assembly'); #4 = APPLICATION_CONTEXT('EUCLID'); #5 = APPLICATION_PROTOCOL_DEFINITION('CommitteeDraft','automotive_design ',1997,#4); #6 = SHAPE_DEFINITION_REPRESENTATION(#7,#11); #7 = PRODUCT_DEFINITION_SHAPE('void','void',#8); #8 = PRODUCT_DEFINITION('void','void',#9,#10); #9 = PRODUCT_DEFINITION_FORMATION('ID','void',#2); #10 = PRODUCT_DEFINITION_CONTEXT('as proposed',#4,'First_Design'); #11 = ADVANCED_BREP_SHAPE_REPRESENTATION('',(#12),#18620); #12 = MANIFOLD_SOLID_BREP('',#13); #13 = CLOSED_SHELL('',(#14,#291,#3567,#3629,#3762,#3869,#4146,#7477, #7539,#7672,#7779,#7807,#7835,#7998,#10155,#12312,#12461,#12610, #14726,#16765,#16844,#17057,#17221,#17365,#17502,#17591,#17752, #17847,#18042,#18071,#18165,#18278,#18327,#18393,#18540,#18606, #18613)); #14 = ADVANCED_FACE('',(#15),#30,.T.); #15 = FACE_BOUND('',#16,.T.);

Data Flow Diagram Maximal Surface/Edges Detection STEP File Geometric Interaction Detection Unique B-Rep Model Generation of Homographs 3D Geometric CI Graph Conventional Interfaces Taxonomy Elimination of Homographs Using Ref State 1 Functional Designations Taxonomy Function CI Graph (all possible homographs) Matching with Functional Designations Functional Designations (multiple suggestions) Annotated ModelUser Functional Designations Interpretations Internal Efforts Screws Elimination of Homographs Using Ref State 2 Kinematic Screws Kinematic Constraints Function CI Graph (less homographs) Eliminating Multiple Candidates Functional CI Graph (least homographs)

Geometric Analysis Using B-Rep the same object might be represented differently, as the same face might be divided into more than one without changing the geometry. Same for the edges. To guarantee a unique representation and the independence of the modeling process, we first convert the B-Rep model into maximal surfaces and edges, which represent the product intrinsically. Hyper-graph

Data Flow Diagram Maximal Surface/Edges Detection STEP File Geometric Interaction Detection Unique B-Rep Model Generation of Homographs 3D Geometric CI Graph Conventional Interfaces Taxonomy Elimination of Homographs Using Ref State 1 Functional Designations Taxonomy Function CI Graph (all possible homographs) Matching with Functional Designations Functional Designations (multiple suggestions) Annotated ModelUser Functional Designations Interpretations Internal Efforts Screws Elimination of Homographs Using Ref State 2 Kinematic Screws Kinematic Constraints Function CI Graph (less homographs) Eliminating Multiple Candidates Functional CI Graph (least homographs)

Conventional Interfaces The result of the geometric interaction between neibouring components. Can be one of the following: –Interference; –Contact; and –Clearance. Reflect the conventions of idealization. Interference Clearance Contact

Geometric Analysis 1.Input: the product’s DMU as Maximal Surfaces and Edges B-Rep. 2.Reference surfaces: locate functional surfaces (canonical shapes). 3.Identify CI: detect interference, contact, or clearance zones.

Geometric Analysis The model is then represented as Geometric Conventional Interface Graph, where: –Nodes are components; –Edges are geometric interaction. Solid Model Geometric CI Graph

Data Flow Diagram Maximal Surface/Edges Detection STEP File Geometric Interaction Detection Unique B-Rep Model Generation of Homographs 3D Geometric CI Graph Conventional Interfaces Taxonomy Elimination of Homographs Using Ref State 1 Functional Designations Taxonomy Function CI Graph (all possible homographs) Matching with Functional Designations Functional Designations (multiple suggestions) Annotated ModelUser Functional Designations Interpretations Internal Efforts Screws Elimination of Homographs Using Ref State 2 Kinematic Screws Kinematic Constraints Function CI Graph (less homographs) Eliminating Multiple Candidates Functional CI Graph (least homographs)

The CI Taxonomy A hierarchy of all possible geometric configurations. –Each leaf in the hierarchy defines unambiguously a particular geometrical configuration called lexeme.

The IC Taxonomy Lexeme: is the smallest meaningful geometric configuration. Those are the leaves of the hierarchy. One lexeme can be interpreted in more than one functional meaning, we call interpretations that map to the same geometric configuration homographs. More than one lexeme may have the same functional interpretation, we call those lexemes synographs. Homographs and synographs are the result of non- standard idealization of geometric congiguration.

The CI Taxonomy For each lexeme the taxonomy defines: –A coordinate system w.r.t. the geometry. –A set of all possible interpretations (homographs). Semi-closed Cylindrical Contact Homographs Loose Shaft Linkage Complete Coaxial Cylindrical Contact Homographs Spline Likage Threaded Linkage Example of two lexemes and their associated interpretations

Generation of 3D Homographs In the Geometric Conventional Interface Graph we map each edge to its lexeme in the taxonomy and replace it with all related homographs, generating the Functional Conventional Interface Graph. Taxonomy of Conventional Interfaces Geometric Conventional Interface GraphFunctional Conventional Interface Graph

Data Flow Diagram Maximal Surface/Edges Detection STEP File Geometric Interaction Detection Unique B-Rep Model Generation of Homographs 3D Geometric CI Graph Conventional Interfaces Taxonomy Elimination of Homographs Using Ref State 1 Functional Designations Taxonomy Function CI Graph (all possible homographs) Matching with Functional Designations Functional Designations (multiple suggestions) Annotated ModelUser Functional Designations Interpretations Internal Efforts Screws Elimination of Homographs Using Ref State 2 Kinematic Screws Kinematic Constraints Function CI Graph (less homographs) Eliminating Multiple Candidates Functional CI Graph (least homographs)

Reference States and Dualities Two reference states: 1.The product is mechanically isolated; no external forces. Model interactions between components characterizing internal forces. 2.The product is kinematically operational; user’s input of a kinematic constraints. Relate to two dualities, respectively: 1.Geometry/Force duality. 2.Geometry/Mobility duality.

Mechanical & Functional Analysis At this stage we are interested in Mechanical & Function Analysis process. The objective of this process is to interpret the geometrically described conventional interface, into a function interface with precise physical and kinematic properties. Ideally this process maps each geometrical interaction with one functional interface, however, the algorithm may converge with one interactions still be mapped to more than one interface, because of the lack of standards. If no valid functional configuration can be inferred, model inconsistency is assumed.

Inference Step 1 Engine Torque Water Pressure

Inference Step 2 Kinematic class 1: Motionless. Kinematic class 2: Rotational motion around the axes. Kinematic class 1: Idealized part. Fixed Rotation

The CI Taxonomy Each interpretation is characterized by two structures defining constraints on each of internal efforts screw and kinematic screw. Constraints are : null (0), strictly positive (+), strictly negative (-), non-null (±), or arbitrary (x). Threaded Linkage Internal EffortsKinematic Spline Linkage Planar Support

Mechanical & Functional Analysis Mechanical analysis is used to eliminate homographs who invalidate one of the two reference states. Physical and kinematic properties of each interpretation is described using screws. For each combination of (not yet eliminated) interpretation, that we can an assumption, we check its validity as follows –Transform all the screw to the same coordinate system (rotations). –Translate all screws to the same origin. –Nullify the sum of all screws. –The assumption is valid iff the nullification along with the constraints on the screws does not imply inconsistency.

Mechanical & Functional Analysis The algorithm: –Apply CI Taxonomy suggestion to the Geometric CI graph, replacing each edge ( lexeme ) by all its possible interpretations ( homographs ). –Initially, all nodes are open. –Until ( all nodes are closed ) Among open nodes, choose a node with smallest number of valid assumptions. Using Ref. State (1 or 2), eliminate interpretations that lead to inconsistency. Recalculate number of valid assumptions. If ( number of valid assumptions is one, or no interpretation was eliminated ) –Mark node as closed ( not open ). If ( no more valid interpretation ) –Report inconsistent model. Where –Our Graph is a pseudo-graph, i.e. parallel edges are allowed. –Number of valid assumptions is the product of number of remaining interpretations over all the interfaces involving a node.

Reasoning Using Screws Planar Contact Complete Cylindrical Interference Complete Cylindrical Contact Planar Contact Complete Cylindrical Contact Planar Contact Complete Cylindrical Interference (3  2) Spline Linkage Threaded Linkage Planar Contatc (1  2) Planar Support Complete Cylindrical Interference (3  2) Spline Linkage Threaded Linkage Planar Contatc (1  2) Planar Support Complete Cylindrical Interference (3  2) Spline Linkage Threaded Linkage Spline LinkageThreaded Linkage Planar Support

Reasoning Using Screws Planar Contact Complete Cylindrical Interference Complete Cylindrical Contact Planar Contact Threaded Linkage Planar Support Threaded Linkage Spline Linkage Planar Support Loose Shaft LinkTight Shaft Link Complete Cylindrical Contact Loose Shaft LinkTight Shaft Link Physical Analysis leads to multible interpretations. This may be eliminated by the kinematic analysis.

Data Flow Diagram Maximal Surface/Edges Detection STEP File Geometric Interaction Detection Unique B-Rep Model Generation of Homographs 3D Geometric CI Graph Conventional Interfaces Taxonomy Elimination of Homographs Using Ref State 1 Functional Designations Taxonomy Function CI Graph (all possible homographs) Matching with Functional Designations Functional Designations (multiple suggestions) Annotated ModelUser Functional Designations Interpretations Internal Efforts Screws Elimination of Homographs Using Ref State 2 Kinematic Screws Kinematic Constraints Function CI Graph (less homographs) Eliminating Multiple Candidates Functional CI Graph (least homographs)

Matching with Functional Designations At this phase, each component will be given be given a functional designation, based on the functional interfaces it has. The Functional Designation Taxonomy is used to this end. More than one designation may be assigned to one component.

Data Flow Diagram Maximal Surface/Edges Detection STEP File Geometric Interaction Detection Unique B-Rep Model Generation of Homographs 3D Geometric CI Graph Conventional Interfaces Taxonomy Elimination of Homographs Using Ref State 1 Functional Designations Taxonomy Function CI Graph (all possible homographs) Matching with Functional Designations Functional Designations (multiple suggestions) Annotated ModelUser Functional Designations Interpretations Internal Efforts Screws Elimination of Homographs Using Ref State 2 Kinematic Screws Kinematic Constraints Function CI Graph (less homographs) Eliminating Multiple Candidates Functional CI Graph (least homographs)

Eliminating Multiple Candidates Interfaces may lead more than one possible solution. Criteria are needed to select the most meaningful option: –Mechanical state: minimize the amount of functions per component. –Kinematic state: No internal mobility in the general case.

Conclusions Emphasis is put on the geometric interaction between objects (representing components) rather than the geometric properties of objects themselves. Analysis of DMUs shows the merit of this approach.